Vertically-aligned (VA) LCD is a mode using a negative liquid crystal material and vertical alignment film. When no voltage is applied, liquid crystal molecules are aligned in a vertical direction and black display appears. When a predetermined voltage is applied, the liquid crystal molecules are aligned in a horizontal direction and white display appears. Comparing to the twisted nematic (TN) LCD, the vertically-aligned (VA) LCD provides higher contrast, higher response speed, and excellent viewing angle characteristics for white display and black display. However, the VA LCD still has a critical drawback of a narrow viewing angle. This poses a problem that the application of the VA LCD is limited.
It is known that viewing angle performance of a VA LCD can be improved by setting the orientation of the liquid crystal molecules inside pixels to a plurality of mutually different directions. European Patent Publication Number 0884626-A2 discloses a multi-domain vertically aligned (MVA) LCD having domain regulators for regulating the orientation of a liquid crystal in which liquid crystal molecules are aligned obliquely when a voltage is applied so that the orientation will include a plurality of directions within each pixel.
FIG. 1 shows a pixel layout of a conventional MVA LCD 100 illustrating four pixels thereof. As shown, as the domain regulators, pixel electrodes 120 on a TFT (Thin Film Transistor) substrate are provided with slits 130, and the common electrode on a CF (color filter) substrate is provided with protrusions 140. Note that the domain regulator is provided in each pixel. When a voltage is applied, electric fields oblique to the surfaces of the substrates are produced near the slits 130 and the edges 120a of the electrodes. The inclined surfaces of the protrusions 140 and the oblique electric fields generated between the substrates determine the directions of the liquid crystal molecules in which the liquid crystal molecules are tilted. In each of the pixels, the orientation of the liquid crystal is divided into four directions (as indicated by the arrows shown in FIG. 1) thereby improving viewing angle performance. In the LCD 100, disclination occurs at some particular regions within the pixel that appear darkened (darkened regions are hatched in FIG. 1).
FIG. 2 shows a pixel layout of another conventional MVA LCD 200 illustrating four pixels thereof. As shown, a plurality of slits 230 and protrusions 240 are provided in a pixel for dividing the orientation of the liquid crystal into eight directions (as indicated by the arrows shown in FIG. 2) thereby improving viewing angle performance. In the LCD 200, disclination also occurs at some particular regions within the pixel that appear darkened (darkened regions are hatched in FIG. 2). Note that the total darkened regions in FIG. 2 substantially have twice the total area of the darkened regions in FIG. 1. Therefore, the LCD 200 has a better viewing angle performance but has a lower aperture ratio (i.e., the ratio of the area that can transmit light to the total pixel area).
It is apparently known from those described above that, the more directions into which the orientation of the liquid crystal is divided, generally the better the viewing angle performance can be, but the total area of the darkened regions are also significantly increased.